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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

FUELS  (GENERAL METHODS)                        301

A totally different formula which permits of the calculation of the
calorific value of coals with a high degree of approximation is that proposed
by Goutal,l namely :

p = SaC + <iV,

where p is the calorific power of the fuel as such, C and V are the percentages
of fixed carbon (coke less ash) and volatile matter (less moisture) and a a
coefficient expressing the calorific power (divided by 100) of the volatile
matters and varying with the amount of these volatile matters. To deter-
mine the value to be ascribed to a the percentage V1 of volatile matters
in the fuel supposed free from moisture and ash is calculated by the formula,

V1 =------— ;   the corresponding value of a is then obtained from the

following table :

V1
	a
	V1
	a
	V1
	a
	V1
	a

Less than 5
	IOO
	14
	I2O
	23
	105
	32
	97

5
	145
	15
	117
	24
	104
	33
	96

6
	142
	16
	"5
	25
	103
	34
	95

7
	139
	17
	113
	26
	IO2
	35
	94

8
	136
	18
	112
	27
	IOI
	36
	91

9
	133
	19
	no
	28
	IOO
	37
	88

10
	130
	20
	ICQ
	29
	99
	38
	35

ii
	127
	21
	108
	30
	98
	39
	82

12
	I24
	22
	107
	31
	97
	40
	80

13
	122
	
	
	
	
	
	

2. Calorimetric   Determination   of   the   Calorific   Power.—The

calorimetric or direct methods are undoubtedly to be preferred to those
just mentioned as they give far more certain results.

The numerous forms of apparatus devised for such determinations may
be grouped in three classes : (i) calorimeters in which the combustion takes
place in a stream of air or oxygen at the ordinary pressure, like those of
Favre and Silbermann, Alexejew, Schwackhofer, and F. Fischer; (2)
calorimeters in which the combustion occurs with the aid of an oxidising
substance mixed with the fuel, as in those of Lewis Thompson, Stohmann,
and Parr ; (3) calorimeters in which the combustion is effected with oxygen
at constant volume and very high pressures, known as calorimetric bombs ';
the first such bomb was due to Berthelot and Vieille and on this were based
the more practical and cheaper ones of Mahler, Hempel and Kroeker, which
are the most suitable forms of apparatus for exact determinations.

Only the types most commonly used will be described here.

(a] LEWIS THOMPSON CALORIMETER. This is a very simple apparatus
giving only approximate results comparable among themselves ; it is,
however, still in common use in England, where contracts are made on the
basis of- its indications. It consists (Fig. 34) of a large glass cylinder with

1 Cowiptes Rendus de I'A cad, des Sciences, 1902, CXXXV, pp. 477-479.p is the required calorific value, referred to the pure fuel.